Bitmap blocks

Several consecutive blocks follow the root block. The bitmap blocks form the bitmap for the QNX 4 partition.

One bit exists for each block on the partition; thus one bitmap block is used for every 4096 disk blocks (corresponding to 2 MB of disk space).

If the value of a bit is zero, the corresponding block is unused. Unused bits at the end of the last bitmap block (for which there are no corresponding disk blocks) are turned on.

Bit assignments start with the least-significant bit of byte 0 of the first bitmap block—which corresponds to QNX 4 block #1.